There are several ways you can damage your career.

Change Jobs very fast: A candidate who changes jobs too fast is considered unreliable. It is ideal to stick with a job for at least 2-3 years before making a change. Three years is the best bet. Any candidate who shifts jobs within 3 years on a regular basis will have tough chances in commanding a good salary package along with bonus etc. Candidates generally realize this late in their career, at a time when they have changed more than seven, eight, ten jobs. It becomes too late then, for them to command a seven-eight digit salary. Hence sticking to a job is an important part of making a truly memorable career. 

Change Sectors: This holds true particularly for those who have stuck to a sector for very long. A marketing executive from the FMCG sector should stick to the sector. This is especially if he wants to do very well. The general tendency for any highly qualified job is that once you begin in a sector it is best to remain in the sector. Word of mouth and goodwill is invariably generated for a candidate who sticks to a particular sector. It is best to stick to a sector like Telecom, Banking, Advertising, Interior Design, Shipping, Media, Ecommerce. Often while dealing with candidates there are specific job functions like Export Documentation wherein candidates are required only from the shipping/manufacturing sector.  

Take long breaks: Any candidate who has taken long gaps between jobs will find it difficult to come back to the job market. He will also generate the same amount of salary. Female candidates tend to take a break from their work during and after pregnancy. Some continue their leave until the child is of a certain age. Men are expected to return to work at the earliest. This is because they monetarily support the family. Taking breaks between two jobs is fine, but the break should not be for a long period. Any break for over three months between work can be considered as a long break and is most certain to affect the job seeker in his career.

Lie about your Qualifications, Remuneration etc: One of the worst mistakes to make, is to lie about one’s qualifications. Candidates generally lie about their qualifications when they are desperate for work. They lie about their  remuneration in jobs which do not require a background check. Candidates doing sales and other jobs with high attrition rates ( BPO’s ) often lie about their qualifications and even their remuneration. This is a bad habit and is likely to be found out, sooner rather than later. People also lie about their family background, age, personal lives etc.

Reference Checks: A big mistake is candidates often give reference checks which are not relevant. Often the referee being spoken to by the employer, does not have genuine information to share and does not know the job prospect very well. There are also other problems like inadequate information shared by the referee. All these lead to chaos and stop a job prospect from making a  successful transition.